This invention relates to a self-regulating sun-sensitive window that automatically varies its opacity in response to incident solar energy.
In general, such windows derive their variable light transmittance quality from thin liquid films sandwiched between transparent conductive surfaces. The liquid film is responsive to changes in the electric field created by the conductors.
Several devices in the present art incorporate photosensitive devices in conjunction with liquid film devices. For example, U.S. Pat. No. 3,668,861, issued to Mitsui, discloses a watch display in which a photo transistor selects between a liquid crystal display system and solid state display depending on ambient illumination. U.S. Pat. No. 4,083,356, issued to Rajagopal, discloses a nematic liquid crystal window interposed between incident sunlight and a solar energy collector. The Rajagopal window may be controlled manually or in accordance with a desired parameter of the solar energy collector to prevent damaging temperatures in the system.
While it has been recognized that the opacity of liquid crystal films can be varied with a small amount of input energy, a shortcoming of these present art devices is that a remote power source is required to supply the electric field which controls the opacity or reflectivity of the device.
A general purpose sun sensitive window is described in the magazine article "Electronic Liquid Window" at pp. 31-35 and 106 of Radio-TV Experimenter and Science and Electronics, June-July 1969. While it is proposed that a photosensitive device may be used to regulate the opacity of the Radio-TV window, again there is no suggestion that the electric field necessary to alter the opacity may be derived solely from the light source itself by means of such photosensitive device.